Problem: If $x \circledcirc y = 2x-8$ and $x \bigtriangleup y = x(y-8)$, find $(-3 \bigtriangleup 3) \circledcirc -4$.
First, find $-3 \bigtriangleup 3$ $ -3 \bigtriangleup 3 = -3(3-8)$ $ \hphantom{-3 \bigtriangleup 3} = 15$ Now, find $15 \circledcirc -4$ $ 15 \circledcirc -4 = (2)(15)-8$ $ \hphantom{15 \circledcirc -4} = 22$.